perf/x86: Use 0xff as pseudo code for fixed uncore event

Stephane Eranian suggestted using 0xff as pseudo code for fixed
uncore event and using the umask value to determine which of the
fixed events we want to map to. So far there is at most one fixed
counter in a uncore PMU. So just change the definition of
UNCORE_FIXED_EVENT to 0xff.

Suggested-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1340780953-21130-1-git-send-email-zheng.z.yan@intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>